Stabilizing composition for olefin polymers containing a hydrocarbon-mercapto-hydrocarbon phosphite,carbon black,and a hindered phenol



US. Cl. 252-4ti0 18 Claims ABSTRACT OF THE DISCLOSURE An olefin polymer stabilizer composition comprising in combination a hydrocarbon-mercapto-hydrocarbon phosphite, carbon black and optionally a hindered phenol.

This application is a continuation-in-part of application Ser. No. 519,415, filed Jan. 10, 1966 now abandoned This invention relates to compositions useful in the enhancement of the resistance of olefin polymers, such as ethylene polymers, to deterioration in physical properties due to heat, comprising a hydrocarbon-mercaptohydrocarbon phosphite in combination with carbon black,

and optionally, a hindered phenol, and to olefin polymer compositions having an enhanced resistance to heat deterioration, due to incorporation therein of such compounds, and to a process of enhancing the resistance of olefin polymers to heat deterioration.

Many of the most important applications of polyethylene such as its use in cable sheathings depend upon its superior physical properties, as evaluated by low temperature brittleness, tensile strength and abrasion resistance tests coupled with good water repellency. Other uses take advantage of its high dielectric strength in applications such as primary insulation of wire conductors.

Unfortunately, however, polymeric materials such as polyethylene are subject to deterioration in air and Weather from sunlight, i.e., ultraviolet radiation, and heat, both of which induce oxidation of the polyethylene and thereby lead to increased brittleness at low temperatures and reduced tensile strength and dielectric properties.

In addition, when polyethylene is mechanically Worked in the presence or absence of air at the elevated temperatures necessary for processing, molecular structure changes occur wherein the polymer becomes lower in tensile elongation, and the original electrical resistivity of the polymer at high and low frequencies becomes progressively poorer. At the same time, undesirable changes occur in both the viscous and elastic components of melt flow behavior. Furthermore, cross-linking occurs upon prolonged exposure of the polymer to ultraviolet radiation in the presence of air.

It is customary to incorporate small amounts of finely dispersed particles of carbon black into polyethylene to shield it from the deleterious degradative effects of ultraviolet radiation, and thereby enhance its resistance to light deterioration. Furthermore, many compounds, socalled thermal stabilizers or antioxidants, have been developed and incorporated as well, to enhance the resistance of polyethylene to thermal and oxidative degradation, such as various amines, diaryl mono-sulfides, phenolic compounds, organic phosphites, and the like.

In view of the knowledge that certain carbon blacks when incorporated into essentially saturated hydrocarbon polymers also act as a mild thermal stabilizer, it might 3,42,375 Patented Aug. 19, 1969 be expected that the incorporation of known stabilizer into polymeric materials containing such carbon blacks would result in increased stability against thermally induced deterioration. It was discovered many years ago, however, that not only is the effect of the presence of such stabilizers and carbon black in the polymer not necessarily additive, but that the efiectiveness of many stabilizers in the presence of carbon black can be and is reduced severalfold. In many instances the stabilizer is rendered completely ineffectual so that such a product has no more resistance against thermal or oxidative degradation than does a sample containing no stabilizer Whatever. For a discussion of the reduction in activity of or complete inefiectiveness of many thermal antioxidants such as diphenyl-p-phenylenediamine or the hindered phenol, 2,2-methylenebis-(4-methyl-6-t-butylphenol), in combination With carbon black, see Journal of Applied Polymer Science, vol. 1, pp. 37 to 42 and pp. 43 to 49 (1959).

A class of compounds has been discovered which when combined with carbon black in polyolefin compositions, such as polyethylene, produce compositions having an enhanced resistance to deterioration in physical properties due to exposure to heat, despite the presence of carbon black.

In accordance with the instant invention, a stabilizer system for polyolefins is provided consisting essentially of a hydrocarbon-metcapto-hydrocarbon phosphite in combination with carbon black, to improve resistance of the polyolefins to heat-induced deterioration, for long periods of time. Such a combination displays a surprising stablizing action against heat-induced deterioration, in view of the presence of the carbon black, suggesting that each component synergizes the stabilizing action of the other. This is especially surprising in View of the fact that in combination with carbon black the elfectiveness of most commercially available antioxidants is decreased.

The special properties of the hydrocarbon-mercaptohydrocarbon phosphite-carbon black combination are enhanced when it is combined with a hindered phenol. The Journal of Applied Polymer Science article cited hereinbefore describes the deleterious effects that carbon black has on the hindered phenol, 2,2'-methylenebis(4-methyl- 6-t-butyl phenol), which alone (without carbon black) gives good protection to polyethylene against heat-induced deterioration but which with carbon black is practically ineffective. In the presence of the hydrocarbon-mercaptohydrocarbon phosphite, however, the combination of the carbon black with the hindered phenol not only does not destroy the effectiveness of the phenol but synergizes the effectiveness thereof, so that the three component combination is more effective than any of the components or pairs of components thereof, taken separately. This is a surprising result, that could not have been predicted even from the efiectiveness of the combination of carbon black and hydrocarbon-rnercapto-hydrocarbon phosphite.

Thus, also in accordance was the instant invention, a preferred composition of the invention is provided, consisting essentially of a combination of a hydrocarbonmercapto-hydrocarbon phosphite, carbon black, and a hindered phenol, which combination is more efliective than any of the components or pairs of components thereof in enhancing the resistance of olefin polymers, such as ethylene polymers, to deterioration in physical properties upon exposure to heat.

In addition, in accordance with the instant invention, olefin polymer compositions are provided, such as ethylene polymer compositions, consisting essentially of the olefin polymer in combination with a hydrocarbon-mercapto-hydrocarbon phosphite and carbon black, and preerably consisting essentially of the olefin polymer in hindered, i.e., substituted in both positions ortho to the combination with the hydrocarbon-mercapto-hydrocarbon phosphite, carbon black and a hindered phenol.

Further, in accordance with the instant invention a process for enhancing the resistance of olefin polymers, such as ethylene polymers, to deterioration of physical properties upon exposure to heat is provided, which comprises incorporating in the olefin polymer a combination of a hydrocarbon-mercapto-hydrocarbon phosphite and carbon black, and preferably a combination of the hydrocarb'on-mercapto-hydrocarbon phosphite, carbon black and a hindered phenol.

The hydrocarbon-mercapto-hydrocarbon phosphites in accordance with the invention can be defined by the formula:

OX1 P oXz in which at least one of the X radicals is R (S-A) and the others can be hydrogen, an organic radical, R having from one to thirty carbon atoms, or R (SA) Accordingly, the hydrocarbon-mercapto-hydrocarbon phosphite of the invention can be a mono, di-, or tri-substituted mercapto neutral or acid phosphite, although the tri-substituted neutral phosphite containing three RSA groups is preferred. Furthermore, a mixture of mono-, diand/or tri-substituted neutral or acid phosphites can be employed herein. A is an alkylene or alicyclene or arylene or a mixed alkylene-alicyclene or alkylene-arylene group in any combination, having a straight or branched chain, whose total number of carbon atoms ranges from one to eighteen, n is one to four, and R is an organic radical and can be selected from the group consisting of aryl, alkyl, cycloalkyl, aralkyl, alkaryl, alkoxy, aryloxy, and heterocyclic groups, in any combinations. Usually, the phosphite will not have more than about sixty carbon atoms.

As typical R radicals there can be mentioned methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isoamyl, hexyl, octyl, isooctyl, 2-ethyl hexyl, nonyl, tetradecyl, octadecyl, lauryl, decyl, palmityl, stearyl, oleyl, benzyl, aand B-phenethyl, xylyl, tolyl, naphthyl, cyclopentyl, cyclohexyl, cyclodecyl, furyl, tetrahydrofurfuryl, thienyl, methoxy, ethoxy, propoxy, isopropoxy, Z-ethyl hexyloxy, decyloxy, dodecyloxy, benzyloxy, phenoxy and the like.

A can be a single bond, as in diphenyl, or a bivalent group, such as:

4 Examples of mono-substituted mercapto phosphites suitable for use herein include, but are not limited to,

mono- B-laurylthioethyl phosphite, mono-isooctylthio-tert-butyl phosphite, mono-diphenylthiomethyl phosphite, mono-2-ethyl-hexylthioethyl phosphite, mono-tolylthio-tz-methyl-ethylphosphite, mono-cyclohexylthiomethyl phosphite, mono-decylthio-decyl phosphite, mono-methoxy thioethyl phosphite.

Examples of di-substituted mercapto phosphites suitable for use herein include, but are not limited to,

di-(Z-ethylhexylthioethyl) phosphite,

(ethyl)-(mono-2-ethylhexylthioethyl) phosphite,

(mono-methylthioethyl) (mono-isooctyl-thioethyl) phosphite,

(methyl) (mono-isooctylthioethyl) phosphite,

(mono-phenylthioethyl) (mono-2-ethylhexylthiomethyl) phosphite,

(2-ethylhexyl) (monophenylthioethyl) phosphite,

di(phenylthioethyl) phosphite,

di-cyclohexylthiomethyl) phosphite,

(monophenylthiononyl) (monotolylthio tit-methyl ethyl) phosphite,

di(decylthiododecyl) phosphite,

(decyl) (mono-decylthiododecyl) phosphite,

di(benzylthiostearyl) phosphite,

di(palmitylthio a-methyl ethyl) phosphite and di(methoxythioethyl) phosphite.

Preferably, the trisubstituted mercapto phosphite is tri (fl-laurylthioethyl) phosphite. Other suitable tri-phosphites include, but are not limited to, tri(isooctylthio butyl) phosphite, (monophenylthioethyl) (di-Z-ethylhexylthioethyl)phosphite, (2 ethylhexyl diphenylthiomethyl) phosphite, (isopropyl) (di-isooctylthiomethyl) phosphite, (di-isooctylthiomethyl) (monotolylthio amethyl ethyl) phosphite, tri(Z-ethyl-hexylthioethyl) phosphite, (phenyl thioethyl) (dicyclohexyl thioethyl) phosphite, tri(phenylthiononyl) phosphite, (nonyl diphenylthiomethyl) phosphite, tri(decyl-thiododecyl) phosphite, tri(benzylthiostearyl) phosphite, tri(palmitylthio a-methylethyl) phosphite, tri-(methoxylthioethyl) phosphite, tri(phenylthioethyl) phosphite, tri(4-tert butylphenylthio ethyl) phosphite, and tri(Z-methyl-4-tert-butylphenylthioethyl) phosphite.

The terms mercapto and thio are used interchangeably herein.

The hydrocarbon-mercapto-hydrocarbon phosphites can be prepared by known procedures which form no part of the instant invention. Thus, for example, they can be readily prepared by reaction of the appropriate a,walkylene chlorohydrin to form a thio-alcohol which is subsequently transesterified using triphenyl phosphite plus sodium ethylate to form the corresponding hydrocarbonmercapto-hydrocarbon phosphite.

These are known reactions and form no part of the instant invention. Furthermore, the reaction product can be composed of a mixture of mono-, diand/or tri-substituted neutral or acid phosphites, which as indicated hereinbefore, can also be employed in the instant invention.

Carbon black suitable for use herein includes both activated or unactivated types, such as channel carbon black, furnace carbon black, animal or vegetable carbon black, thermal carbon black, light lamp blacks, acetylene blacks and the like, and carbon blacks activated in the presence of such materials as oxygen, sulfur or selenium. The average particle size of carbon black used herein should be below about 1000 angstroms, and preferably below about 200 angstroms, so as to ensure the obtention of a uniform dispersion of the carbon black through the polymer.

The phenols which can be used herein should be hydroxyl group, and can contain from about eight to about 300 carbon atoms. Such phenols can be monocyclic or polycyclic, and monohydric or polyhydric.

The hindered monocyclic phenols which can be employed have the structure:

R is selected from the group consisting of halogen; and organic radicals containing from one to about thirty carbon atoms, such as alkyl, aryl, alkenyl, alkaryl, aralkyl, cycloalkenyl, cycloalkyl, alkoxy, aryloxy and acyl where R is aryl, alkyl or cycloalkyl.

x is an integer from two to four, and x is an integer from one to four, and the sum of x and x does not exceed six. The monocyclic phenol containing one or more hydroxyl groups should be substituted in both positions ortho to each hydroxyl group.

Polycyclic phenols include aromatic nuclei which are linked by a bivalent linking radical, and are defined by t rm,

( om L l- 0111,

wherein R R and R are inert substituent groups of the type of R above, Y is a bivalent linking radical, and is selected from the group consisting of oxygen atoms or an alkylene or alicyclene or arylene or a mixed alkylenealicyclene or mixed alkylene-arylene groups having a straight or branched chain, whose total number of carbon atoms ranges from one to about eighteen. m is an integer from one to a maximum of 5(z +y m can be an integer from zero to three; and m an integer from one to four; 2 can be an integer from zero to about six, and Z an integer from one to five, preferably one or two. Preferably, the hydroxyl groups in polycyclic phenols are located ortho and/or para to Y. There can be from one to four hydroxyl groups per phenyl nucleus, y y and y representing the numbers thereof, each phenyl nucleus being substituted in both positions ortho to each hydroxyl group. Preferably, there will be only one hydroxyl group per phenyl nucleus.

Y can be a single bond, as in diphenyl, or a bivalent group, such as:

CH3 3H1 2115 Representative phenols include 2,6-di-tert-butyl-4- methyl phenol, 2-tert-butyl-6-methoxy phenol, 2,6-dinonyl phenol, 2,3,4,6-tetradecyl phenol, 2-isopro'pyl-6- dodecyl phenol, 2-methyl-6-octyl phenol, 2-hexyl-6-ndecyloxy phenol, 2-nonyl3-methyl-6-n-decyloxy phenol, and 2 nonyl 6 benzyloxyphenol, 2,6-di-tert-butyl-2- methoxy-p-cresol (Antioxidant 762) and 3,5-di-tert-butyl- 4-hydroxybenzyl ether.

Exemplary polyhydric monocyclic phenols are: 2-ethyl- 4-octyl-6-methyl resorcinol, 2-dodecyl-4-methyl-6-nonylresorcinol, 2 methyl-4-isooctyl-6-dodecyl-phloroglucinol, 2,4,6-tri-tert-butyl resorcinol, and 2,4,6-triisopropyl phloroglucinol.

Exemplary polyhydric polycyclic phenols are 2,2- methylenebis (6-tert-butyl-phenol), 2,2-methylene-bis (4- methyl-6-tert-butyl-phenol) (Cyanamid 2246), 4,4- methylene bis (2,6-di-tert-butyl-phenol) (Ethyl Antioxidant 712 or Ionox 220), 2,2-methylene-bis(4-ethyl-6- tert-butyl-phenol) (Cyanamid 162), 4,4'-methylene-bis(6- tert butyl-o-cresol) (Ethyl Antioxidant 220), 4,4-oxobis (2-methyl-6-isopropyl phenol), 2,2'-oxobis(6-dodecyl phenol), 4,4 n-butylidenebis(2-tert-butyl-6-methylphen01), 4,4 benzylidenebis(Z-tert-butyl-6-methylphenol), 4,4-cyclohexylidenebis(2,6-di tert butyl phenol), 1,3,5- trimethyl 2,4,6 tris(3,5-di-tert-butyl-4-hydroxy benzyl benezene) (Ionox 330), 2,2-methylenebis(4-methyl-6-(1- methyl cyclohexyl)-phenol), 2,6-bis(2'-hydroxy-3-tertbutyl 5' methylbenzyl)-4-rnethylphenol, 1,1,3tris(2- methyl-4'-hydroxy-5'-tert-butylphenyl)butane and 03,06 bis 3-tert-butyl-5-methyl-2-hydroxy-phenyl -mesitol.

The preferred stabilizer system of the invention comprises two or three stabilizers, the hydrocarbon-mercaptohydrocarbon phosphite and carbon black, and optionally a hindered phenol. These two and three stabilizers together can display a stabilizing effectiveness which is not depressed by the carbon black, and which can exceed that obtainable from any of them alone, or in combinations of two. On the other hand, however, when the hindered phenol alone is employed with carbon black, the hindered phenol loses almost all of its antioxidant effectiveness, and accordingly the synergistic result using the three component combination is especially unexpected. This enhanced stabilizing eifect is obtained with any olefin polymer, regardless of the process by which it is prepared.

A suflicient amount of the stabilizer combination of the invention is used to enhance the resistance of the olefin polymer against deterioration in physical properties, including, for example, resistance to embrittlement upon exposure to heat under the conditions to which the polymer will be subjected. Small amounts are usually adequate. Amounts of the hydrocarbon-mercapto-iydrocarbon phosphite within the range from about 0.002 to about 0.5% by weight of the olefin polymer and amounts of car bon black within the range from about 0.2 to about 5% by weight of the olefin polymer are satisfactory. For many polyethylene applications, carbon black concentrations of up to about 50% can be present, especially Where partially conductive polyolefin-carbon black compounds are employed. Preferably, from about 0.05 to about 0.15% of the hydrocarbon-mercapto-hydrocarbon phosphite and from about 2 to about 3% of the carbon black are employed for optimum enhancement of resistance to heat deterioration.

The hindered phenol can be used in quantities as low as about 0.002%, and as high as about 0.5% by weight of the olefin polymer, and preferably in amounts from about 0.02 to about 0.1% by weight of the olefin polymer.

The two component combinations of stabilizers of the invention will generally contain from about 0.05 to about 0.15% of the hydrocarbon-mercapto-hydrocarbon phosphite, and from about 0.3 to about 3.0% of the carbon black. The three component combinations in addition include from about 0.02 to about 0.1% of the hindered phenol, by weight of the combination.

Other thermal stabilizers can be employed in the compositions of the present invention such as organic hydrocarbon phosphitcs, thiodipropionic acid esters, polyvalent metal salts of organic acids, organic polysulfides, aminophenols, and the like. Light stabilizers can be employed in the composition of the instant invention such as various 2-hydroxybenzophenones, thiosalicyclates and the like.

Conventional additives such as fillers, pigments, and plasticizers can also be present.

If a combination of stabilizers is to be utilized, they may be formulated as a simple mixture for incorporation in the polymer by the polymer manufacturer or by the converter. An inert organic solvent can be used to facilitate handling, if the ingredients do not form a homogeneous mixture or solution.

The stabilizer of the invention is applicable to olefin polymers prepared by any of the various procedures, using the available catalysts, such as the Ziegler, ICI, Union Carbide, Du Pont, Phillips, Montecatini, Esso and Standard Oil (Indiana) process polymers (Chem. & Eng. News, Nov. 21, 1960, pp. 3659), inasmuch as the molecular weight and tacticity are not factors atfecting this stabilizer.

Formerly, olefin polymers prepared by these processes contained traces of catalyst residues. These residues materially diminished the stability of the olefin polymer, despite efiorts to overcome the problems by addition of polyvinyl chloride resin stabilizers, Whose function was to act on the halogen or halide of the catalyst in the same manner as on the halogen or liberated halide of the polyvinyl chloride resin. It is now customary to remove catalyst residues substantially completely, so that the addition of polyvinyl chloride resin stabilizers is no longer indicated. The stabilizers of the invention are eifective with olefin polymers substantially free from catalyst residues, although they can also be used with catalyst-containing polymers with good results.

The stabilizer of the invention is particularly applicable to ethylene homopolymers, which include normally solid low or high molecular weight homopolymers obtained from ethylene. Such polymers usually have a molecular weight of at least 6,000 and preferably a molecular weight of 20,000 to 45,000 or more. They have a waxy feel, and when examined by the X-ray diffraction technique exhibit the presence of a crystalline phase.

Mixtures of ethylene homopolymers with other compatible polymers, and copolymers of ethylene with copolymerizable monomers such as styrene, vinyl chloride, vinyl acetate, vinylidene chlorofluoride and methyl methacrylate which are not reactive with the stabilizer combination, the ethylene polymer or copolymer being present in a sufiicient amount, usually a major amount, i.e. about 85% Weight or more, to present the stabilization problem resolved by the invention, also can be stabilized. The term ethylene polymer as used herein includes, accordingly, homopolymers such as low or high density polyethylene, and Ziegler polyethylene and ethylene copolymers, and mixtures of ethylene homopolymers, as discussed above.

The stabilizers of the invention can also be used with other olefin polymers, such as polypropylene, poly(butene-l), poly(pentene-l), poly(3-methyl butene-l), poly- 4-methyl-pentene-l, and polystyrene.

The term olefin polymer encompasses both homopolymers and copolymers, as well as mixtures of olefin polymers.

The stabilizer is incorporated in the polymer in suitable mixing equipment, such as a mill, a Banbury mixer, an

extruder and the like. If the ethylene polymer has a melt viscosity which is too high for the desired use, the ethylene polymer can be worked until its melt viscosity has been reduced to the desired range, before addition of the stabilizer. The resulting mixture is then removed from the mixing equipment, and brought to the size and shape desired, for marketing or use.

The stabilized olefin polymer can be Worked into the desired shape, such as by milling, calendering, extrusion, or injection molding or fiber-forming.

The term consisting essentially of, as used herein, means that the ingredients recited in the specification and claims are the essential ingredients of the composition of the invention and no others are employed which would be undesirable in the enhancement of the resistance of olefin polymers to deterioration in physical properties due to exposure to heat.

The following examples in the opinion of the inventors represent the best embodiments of their invention.

Example 1 The two-component hydrocarbon-mercapto-hydrocarbon phosphite-carbon black stabilizer system of the invention was evaluated for the stabilizing effect of each component thereof, taken singly, and in a pair, in enhancing the resistance of polyethylene to deterioration in physical properties due to exposure to heat. The stabilizers used were tri(fl-laurylthioethyl)phosphite and carbon black, in the form of channel carbon black having an average particle size of about 20 A. Stabilizers were weighed and dispersed in previously unstabilized polyethylene (NH 323), melt index 0.15 ASTM D1238-62T at 190 C., using a two-pound laboratory Banbury mixer. The mixture was placed in a cold roll mill and Was flattened and the crepe produced cut to convenient size for subsequent tests. Table I below sets forth the stabilizers contained in each of the various samples of polyethylene prepared. Although Control Sample A did not contain stabilizers or carbon black it was subjected to the same preparatory mixing as the other samples.

The eifectiveness of this stabilizer system of the invention in inhibiting increase in melt index (Test A), while maintaining good tensile properties, as evaluated by tensile strength, tensile yield strength, and tensile elongation (Test B), and maintaining good dielectric constant and dissipation factor (Test C) after heat ageing, shows the degree of heat stabilization imparted by the compounds of the invention. All of the above tests were carried out on small samples, which were exposed to prolonged roll milling conducted at 320 F. for various times up to and including 6 hours, or oven ageing at C. for various times up to and including 292 hours.

Test A.Melt index The tri(fl-laurylthioethyl)phosphite-carbon black stabilizer combination of the invention was evaluated for its inhibiting eifect on rate of increase in melt index of polyethylene. Samples were prepared as described and Were oven aged or roll milled for various times. Portions of each sample were then submitted to a melt index determination using the ASTM Dl238-62T procedure at C. Table II below tabulates the results obtained for the various Samples A to D by showing the flow rate (grams/ 10 minutes) of the heat aged samples for each ageing time. The effect on rate of flow of the polyethylene samples over the various ageing times corresponds to the efiect on melt index over the same ageing periods and thus is an accurate measure of resistance to heat deterioration imparted by the stabilizer added to the polymer.

TABLE II [Melt Index (g./ m1n.)]

Oven Aged (at 100 0.) Minutes on 320 F. R011 Mill Before Test Sample No Ageing 72 hrs. 146 hrs. 292 hrs. 6 10 30 60 90 120 180 240 360 A (nnstabilized polyethylene) 0. 23 0. 08 0. 12 17. 7 0. 09 0. 05 004 0. 07 0. 08 0. 10 0. 04 B (polyethylene and carbon black) 0. 16 0. 16 0. l5 0. 20 0. 16 0. 16 0. 16 0. 16 0. 17 0. 17 0. 26 0. 22 O (polyethylene and tr1(B-laurylthioethyl)phosphite) 0. 14 0. 13 0. 11 0. 11 0. 11 0. 09 0. 24 0. 28 0. 10 0. 0. 21 0. 08 0. 08 D (polyethylene tri(B-laurylthioethy1) phosphite and carbon black) 0. 16 0. 15 0. 14 0. 15 0. 16 O. 18 0. 18 O. 19 0. 17 0. 18 0. 18 0. 24 0. 25

The effectiveness of the stabilizer system of the invention (Sample D) in inhibiting change in melt index is evident from the data of Table H.

Test B.--Tensile properties The results tabulated in Tables III, IV and V clearly show that this stabilizer composition of the invention enhanced the resistance of polyethylene against decrease in tensile strength, decrease in tensile yield strength and decrease in tensile elongation due to heat ageing.

Test C.--Dielectric properties The dielectric constant (using testing procedure ASTM D153l-62) and dissipation factor (using testing procedure ASTM D153 1-62) of Samples A to D were measured after various periods of heat ageing and the data obtained is reported in Tables VI and VII respectively.

TABLE III [Tensile Strength (p.s.i.) at Break] Oven Aged 0.)

Roll Milled (320 F.)

Sample Ageing 72 hrs. 146 hrs. 292 hrs. 1 hr. 2 hrs. 3 hrs. 4 hrs. 5 hrs. 6 hrs A (nnstabilized polyethylene)- 1, 890 1, 490 1, 230 1, 350 1, 530 1, 420 1, 420 1, 390 1, 330 1, 390 B (polyethylene and carbon black 1, 980 1, 890 1, 870 1, 880 1, 680 1, 750 1, 770 1, 710 1, 780 C (polyethylene and tri(fl-laurylthioethyl) phosphite) 2, 040 1, 860 l, 760 1, 660 1, 640 1, 420 1, 450 1, 340 1, 410 1, 310 D (polyethylene tri(fl-laurylthioethyl)phos phite and carbon black)- 1, 980 1, 760 1, 830 1, 770 1, 960 2, 040 1, 920 1, 900 2, 040 1, 920

TABLE IV [Tensile Yield Strength p.s.i.]

N Oven Aged (100 C.) Roll Milled (320 F.)

Sample Ageing 72 hrs. 146 hrs. 292 hrs. 1 hr. 2 hrs. 3 hrs. 4 hrs. 5 hrs. 6 hrs.

A (unstabilized polyethylene). 1, 400 1, 490 1, 450 1, 640 1, 530 1, 460 1, 420 1, 400 1, 390 1, 430 B (polyethylene and carbon black) l, 400 1, 590 1, 530 1, 500 1, 470 1, 470 1, 450 1, 440 1, 440 C (polyethylene and tri(fl-laurylthioethyl)- phosphite) 1, 350 1, 460 1, 470 1, 480 1, 410 1, 390 1, 410 1, 380 1, 410 1, 340 D (polyethylene,

phite and. carbon black) 1, 480 1, 500 1, 560 1, 590 1, 500 1, 510 1, 500 1, 530 1, 520 1, 350

TABLE V [Tensile Elongation at Break N Oven Aged (100 0.) Roll Milled (320 F.)

Sample Ageing 72 hrs. 146 hrs. 292 hrs. 1 hr. 2 hrs. 3 hrs. 4 hrs. 5 hrs. 6 hrs.

A (unstabilized polyethylene) 550 475 270 260 230 370 380 250 225 B (polyethylene and carbon black) 570 540 550 610 480 550 500 490 500 C (polyethylene and triQBJaurylthiocthy phosphite) 610 600 560 600 500 420 410 310 310 290 D (polyethylene, tri(5-laurylthioethyl)phosphite and carbon black)- 580 540 560 580 600 540 520 540 540 580 TABLE VI ethylene in improving resistance of polyethylene to em- [Dielectric Constant (100 k.c.)] brittlement at low temperatures (Test D).

The samples were prepared as described in Example 1 fi 232 and then were oven aged at 100 C. for various times up to NO 292 6 and including 292 hours, or were exposed to prolonged Sample Ageing hrs. hrs. hm roll milling conducted at 320 F. for various times up to and including 6 hours.

The three component stabilizer system of the invention 2-522 2520 2-536 2-509 2-507 was evaluated for its stabilizing effect on polyethylene in A (unstabillzed polyethylene) 2.316 2.433 2. 73 2.390 2. 436 B (polyethylene and carbon lack C (polyethylene and tri(fllaurylthloethyl)phosphite- 2. 319 2.328 2. 323 2. 366 2. 415 improving resitance 0f P9 y y changes in P 2 D gg ls tl y e g g gy cal and chemical condition as detected by diiferentlal caigfimblia kg? 2. 536 2.526 2. 551 2.508 2. 501 thermal analysis (Test E). Two different apparatus were employed in this test, namely the Perkin Elmer Differential Scanning Calorimeter and the Du Pont 900 DTA equipped 1 with a 900 250 time base accessory.

Table VIII below sets forth the stabilizers contained in each of the various samples of polyethylene prepared.

TABLE VIII [In Percent] Stabilizer System D E F Control 1 Control 2 Control 3 Control 4 Control 6 Control 6 Control 7 Carbon Black 5 2- 5 2. 6 Trl(fl-laurylthioethyl)phosphite 0. 1 I

4,4-methylenebis(2,6di-tert-butyl phenol) 4,4'-th1obis(2-tert-butyl-5-methyl phenol) TABLE VII [Dissipation Factor (100 k.c.)]

688 25 g Samples D, E and Controls 1 and 2 were submitted to Tests A to C as described in Example 1. The results of No 146 292 3 6 Sample Ageing hrs. hrs. hrs. hrs. these tests follow A(unstabilized polyethylene) 0.0014 0.0053 0.0092 0.0028 0.0042 B (polyethylene and carbon black) "(112 .68 0.0016 0.0015 0.0018 0.0015 0.0015

01 eth lene an r1 l iiry lthi othybphosphite)---- 0.0014 0.0015 0.0002 0.0025 0.0037 D (polyethylene, jtrKB-laurylthl hos hite and carl )%%1b 1 3z 3 0.0018 0.0017 0.0019 0.0016 0.0012

Test A.Melt index As seen from the results in Table IX below, the use of the hindered phenol in the three-component combination of Sample E did not destroy the stabilizing effectiveness The data clearly show that the two-component stabilizer of the other two components, tri(fi-laurylthioethyl)phoscomposition of the instant invention enhanced the resistphite, and carbon black in inhibiting increase in melt index. ance of polyethylene against degradation in dielectric properties due to exposure to heat.

TABLE IX [Melt Index (g./10 mln.)]

Oven Aged (at 100 C.) Minutes on 320 F. Roll Mill Before Test sample No ageing 72 hrs. 110 hrs. 292 hrs. 5 10 so so 90 120 180 240 360 1 th lene, carbon black and trKB-laurylthloiigli gnog nns) 0.16 0.15 0.14 0.15 0.16 0.18 0.18 0.19 0.17 0.18 0.18 0.24 0.25

E (polyethylene, carbon black, trlQB-laurylthlo ethyl)phosphite and 4,4-methyleneb1s(2,0dl-tertbutylpheno1)) 3 17 15 0.16 0.16 0.15 0.18 0.19 0.19 0.21 0.23 0.22 0.31 Control1(4,4-thiobis (2-tert-butyli5met3lyl1phlenol); 0.22 0.19 0.20 0.24 0.23 0.25 0.22 0.24 0.23 0.24 0.26 0.28 0.37

t 12 4,4-th' b's 2-tertbut -5me y p eno $%.i%s.b 0nbn? l- 0-16 .16 0.15 0.16 0.18 0.19 0.24 0.20 0.18 0.19 0.20 0.21 0.2

Example 2 The three-component stabilizer system of the invention, Test B' Tens11e Propmues namely the hydrocarbon mercapto hydrocarbon phosphite, With regard to the results of the tensile properties carbon black and hindered phenol combination, was evalutests: it i dil seen i T bl X h h three-comated f r its Stabililiflg efiect 0T1 P ly y using Tests ponent stabilizer combination of the invention which A to C described in Example 1, against the two-component includes h hi d d h ol (Sample E), is superior to combination of the invention which does not contain the the twmcomponent combination of the invention (Sample hindered phenol and against. a f q available D), in enhancing the resistance of polyethylene to rephenolic f alone m combmatlon Wlth carbon duction in tensile elongation upon exposure to heat. Acblack, 1n enhancing the resistance of polyethylene to deg y, this Shows the hindered phenol (Enhanced the terioration in physical properties due to exposure to heat. The stabilizers used were tri(B-laurylthioethyl)phosphite, f y f of the twoomponem comlimatlon- In 22 11 carbon black (as in Example 1) and the hindered phenol, t'lom 1t 15 56m from the data of C tr0 2 that the a I 1- 4 4-methylene bis (2,6-di-tert-butyl phenol) and a the hon of carbon black to the commercially available throcommercially available antioxidant 4 4'..th bi (2 t t bisphenol of Control 1 adversely alfected the stabilizing 1-5 1 h 1 efiectiveness of the thiobisphenol 1n enhanclng the re- In addition, the three-component stabilizer system of the Sistance of polyethylene to reduction in tensile elongainvention was evaluated for its stabilizing efiect on polytion when oven aged at C. for various times.

TABLE X [Tensile Elongation at Break (percent)] N Oven Aged (100 0.) Roll Milled (320 F.)

Sample Ageing 72 hrs. 146 hrs. 292 hrs. 1 hr. 2hrs. 3hrs. 4hrs. 5hrs. 6hrs.

D (polyethylene, carbon black and triQS-laurylthloethyl) phosphite) 580 540 560 580 500 540 520 540 540 580 E (polyethylene, carbon black, triw-laurylthloethyl)phosphite and 4,4-methylenebis(2,6-di-tertbutyl phenol)) 610 630 630 640 600 550 590 520 610 620 Control 1 (4,4 tlliobis(2-te1t-butyl-5-rnethylphenol)) 610 620 630 620 600 550 580 560 600 630 Control 2 (4,4-thiobis(2-tert-butyl-5-methylphenol) and carbon black) 580 570 580 570 600 620 600 620 550 (320 The data set forth in Tables XI and X11 show that the presence of the hindered phenol in the stabilizer combination of the invention (Sample E) had no substantial deleterious eifect on the stabilizing effectiveness of the hydrocarbon mercapto hydrocarbon phosphite-carbon black combination (Sample D) in enhancing the resist- 15 The results set forth in Table XIV below show that the inclusion of the hindered phenol in the stabilizer composition of the invention (Sample E) did not adversely effect the stabilizing effectiveness of the two-component stabilizer composition of the invention (Sample D) in ance of polyethylene to reduction in tensile strength and enhancing the resistance of polyethylene to degradation in tensile yield strength due to exposure to heat.

dissipation factor.

Oven Aged (100 C.) Roll Milled (320 F.)

No Ageing 72 hrs. 146 hrs. 292 hrs. 1hr.

Sample 2h1's. 3hrs. 4hrs. 5h.rs. ohrs.

D (polyethylene, carbon black and tri(fl-laurylthioethyl) phosphite) l 1,980 1,760 1,830 1,770 1,960 2, 040 1,920 1,900 2, 040 1,920 E (polyethylene, carbon black, t urylthioethyl) phite and 4,4-methylenebis(2,fi-di-telt butyl phenol 1,980 1,940 1,940 2,050 2,000 1, 820 1,870 1, 820 1, 910 1,960 Controll (4,4'-t11iobis(2tert-buty1-5methyl henol. 1,980 1,980 1, 930 1,740 1,900 1,800 1,980 1,880 1,910 2,010 Control 2 (4,4-thi0bis(Z-tert-butyl-dmethyl phenol) carbon black) 1,990 1, 910 1,820 1,750 1,950 2,000 1, 980 1,930 1, 2,930

TABLE X11 [Tensile Yield Strength (p.s.1.)]

N Oven Aged (100 C.) Roll Milled (320 F.)

0 Sample Ageing 72 hrs. 146 hrs. 292 hrs. 1hr. 2hrs. 3hrs. 4hrs. 5hrs. fihrs.

D (polyethylene, carbon black and tritfl-laurylthioethyl) phos hite) 1,480 1,500 1,560 1,590 1,500 1,510 1,500 1,530 1, 520 1,350 E (polyethylene, carbon black, tri(fl-laurylthioethyhphosphite and 4,4-methylenebis(2,6-di-tertbutylphenol)) 1, 390 1,540 1,500 1,580 1, 480 1,300 1,380 1, 310 1,380 1,380 Controll (4,4 -t11iob1s(atert-butyl-smeth l henol 1,380 1, 480 1,470 1,480 1,376 1,350 1,370 1, 300 1,350 1,320 Control 2 (4,4-thiobis(2-tert-butyl-5-methylphenol) and carbon black) 450 1,520 1, 520 1,550 1,500 1,500 1, 490 1,490 1,500 1,490

Test C.Dielectric properties TABLE XIV The results of Table XIII below show that the addltion of the hindered phenol to the two-component com- Dissipation Fa t bination of the invention enhanced the stabilizing etfectiveness of the hydrocarbon-mercapto-hydrocarbon phos- &3??? phite-carbon black combination in enhancing the reslstance N W o of polyethylene to degradation 1n dielectric constant. Fursample ageing hrs. hrs. 3 hm 6 hrs thermore, the results of Control 2 clearly show that the addition of carbon black to the commercially available $3 $ffigfi$f antioxidant, (Control 1) adversely affected its stabilizing phosphite) 0.0018 0.0017 0.0019 0.0010 0.0012

fie ti Hess E (polyethylene, carbon black, 8 C n i m-l ur lth o t n np osp ite an TABLE Km methylenebis(2,6-di-tert- Dielectric Constant (100kc.) butylphenoD) 0.0020 0.0020 0.0021 0.0016 0.0017

Control 1 (4,4-thiobis(2-tert- OvenAged Roll Milled butyl-5-methyl phenol 0.0017 0.0016 0.0014 0.0017 0.0017

(100 0.) (320 F.) Control 2 (4,4-thiobis(2-tertbutyl-5-methyl phenol) and No 146 292 carbonblack) 0.0021 0.0021 0.0020 0.0018 0.0017 Samples ageing hrs. hrs. 3hrs. fihrs. D (p((1)ly?2;hl0I16,1 lglblzlhl b1l)aek an tr aury ioe y phosphi te) 2. 536 2.526 2.551 2.508 2. 501 Test D LOW temperature bntfleness E (pzwlyethylefie, ctalrblon black,

tri fl-aury ioe y phosphite and 4,4'- 7 Samples A, B, C, E and Controls 1 and 2 were evalug gf gfi gfig fi fi j 2510 251 2516 2.480 2483 ated for their effectiveness in improving resistance of Controll(4,4-thiobis(2etert- 2 2 320 2 317 2 318 polyethylene to embnttlement at 76 C. using ASTM 2,31%fi ltfi fitfgigfllgg:--- 2'317 5 D-746-64T testing procedure and the failures per 10 but 1-5-meth 1 henol and s ecimens tested for each of various times of heat ein carll onblackiPuufll 2.543 2. 501 2. 553 2.505 2. 507 p ag g were recorded in Table XV below.

TABLE XV [Low Temperature Brittleness at -76 0. Number of Failures/ Specimens] Oven Aged (100 0.) Roll Milled (320 F.)

Sample No Ageing 72 hrs. 146 hrs. 292 hrs. 3 hrs. 6 hrs.

A (unstabilized polyethylene) l/10 10/10 7/10 10/ 10 B (polyethylene and carbon black) 2/10 2/10 8/10 2/10 0/10 0/10 C (Polyethylene and tri(B-laurylthioethyl)phosphite) 0/10 l/10 4/10 2/10 2/10 7/10 E (Polyethylene, carbon black, tri(B-laurylthioethyl) phosphite and 4,4-methylenebis(2,6-di-tert-butylphenol)) 0/10 0/10 0/10 1/10 1/10 0/10 Control 1 (4,4-tli1obis(2-tert-butyl-5-methyl phenol)). 0/10 0/10 1/10 0/10 1/10 0/10 Control 2 (4,4-thiobis(2-tert-butyl-5-methyl phenol) and carbon black) 0/10 7/10 6/10 9/10 1/10 0/1 The data indicated that the three-component stabilizer C. Thereafter, the nitrogen was replaced by oxygen flowcombination of the invention (Sample E), was superior ing at a rate of 30 mL/min. and the recorder started. When in stabilizing effectiveness to either the carbon black a noticeable break appeared in the trace, the induction (Sample B) or tri(p-laurylthioethyl)-phosphite (Sample time was obtained from the chart speed which was set at C). The results of Control 2 indicated that the addition 0.1 in./min. The results obtained for each sample were of carbon black to the commercially available antioxidant, recorded in Table XVI below.

i.e. the unhindered thiobisphenol of Control 1, completely destroyed the stabilizing effectiveness of this unhindered TABLE XVI thiobisphenol in enhancing the resistance of polyethylene Induction Times to low temperature brittleness. Perkin Elmer Dsifferential D P t Test E.-Differential thermal analysis Sample oai r iffi ir eoo p'i ii The tri(fi -laurylthioethyl) phosphite-carbon black-4,4- $32% g fig ifftfiifiigitfigfifg, fiifgfif methylenebis(2,6-d1-tert-butyl phenol) combination of the y g p 50 113.5 invention was evaluated for its irihibiting effect on changes 33,58 4 82, 1, ,52%? 51551, 8 in physical and chemical condition of polyethylene under- 5 (tri(B-1aury1thio y1)p te 1 gomg dlfierentlal thermal lf control"llji -ifitifyielifiisfbiliiiir'tl In one test method, the Perkin Elmer Differential Scanyl p alone) 8 37 ning Calorimeter was employed. This apparatus is b t 1.?$tiii13fiffil f fil 50 136.5 equipped with a recorded which records the heat or energy changes in the samples undergoing testing as a function As seen from the results in Table XVI above, the three of time (chart speed). When a noticeable break appears component stabilizing combination of the instant invenin the trace recorded, this indicates that the sample has tion was very effective in inhibiting a change in state of undergone a change in condition. The samples tested were the polyethylene undergoing differential thermal analysis. in the form of discs prepared as follows. Film was pressed The induction times obtained using the Perkin Elmer apfrom the resin at a temperature of 125 C. and a pressure paratus were much shorter than that obtained with the of 30 p.s.i. Film discs were cut from the film, the discs 40 Du Pont apparatus. The difference in induction times can having a diameter of about A inch and a thickness rangbe explained from the differences in the type of samples ing from about 2 to about 3 mils. The discs were introused in each apparatus, the cell geometry, and the rate duced into the calorimeter cell and heated from a temof flow of oxygen over the sample surface in each apparaperature of 37 C. to a temperature of about 200 C., at tus. From the data, it is seen that the three component a rate of 80 C./min. in an atmosphere of nitrogen. When stabilizer combination of the invention was substantially the temperature reached 200 C., the nitrogen was reas effective as the combination of the carbon black and placed by oxygen flowing at a rate of 5 nil./min. and the the commercially available thiobisphenol of Control 7. recorder was at that time started. When a noticeable break Furthermore, it is clearly seen that the three component appeared in the trace, the induction time was obtained stabilizer combination of the invention was substantially from the chart speed which was set at 12 inches per hour. more effective as a stabilizer than the individual compo- Table XVI below tabulates the results obtained for the nents thereof in inhibiting change of state of the polyvarious Sample F, and Controls 3 to 7, by showing the ethylene undergoing differential thermal analysis. induction time in minutes for each sample. The reported Examples 3 to 8 induction times are only relative since they are affected by the size, shape, and thickness of the sample, cell The two and three-component stabilizersystems of the geometry, d h t f oxygen fl over th f invention were evaluated for their stabilizing effect on The anti-oxidant induction times of the Sample F and Poly yl improving resistance f polye hyl ne t0 Controls 3 to 7 compositions were also determined by Changes In P y and chemlqal condltlon as detected y using a Du Pont 900 DTA apparatus equipped ith a differential thermal analysis using the Du Pont 900 DTA 900 250 time base accessory. The Du Pont apparatus conequ pped with a 900 250 time base accessory, described tains a recorder which measures temperature as a funcin Example 2. tion of time (chart speed). The apparatus was used as The samples were prepared as described in Examples follows. 0.2 g. pellet samples were placed in a 4 mm. 1 and 2. I diameter sample tube and inserted in the apparatus. Nitro- Table XVII below sets forth the stabilizers contained in gen gas was flowed at a rate of 30 ml./ min. over the sureach of the various samples of polyethylene prepared and face of the sample while the sample was heated to 200 the results obtained.

TABLE XVII Control Example No.

Ingredients 3 4 3 4 5 6 7 s Polyethylene 100 100 100 100 100 100 100 Tri(4-tert-butylphenylthioethyl)phosphite 0. 1 0. 1

Tri(2-methyl-4-tert-butylphenylthioethyl)phosph e Tri(phenylthioethyl)pliosphite Carbon black 4,4-methylenebis(2,6-di-tert butylpheno Induction Times (min.) using DuPont 000 DTA 16 12 10 22 26 167 103 1 7 As seen from the results in Table XVII, the twoand three-component stabilizing combinations of the invention were very efiective in inhibiting a change in condition of the polyethylene undergoing differential thermal analysis.

18 is one to four and A is selected from the group consisting of alkylene, alicyclene, arylene mixed alkylene-alicyclene, and mixed alkylene-arylene groups, and carbon black, each present in an amount to enhance the stabilizing eifect of the other.

xain les to 17 E p 5 2. An olefin polymer stabilizer combination in accord- In Examples 9 to 17, various hydrocarbon-mercaptoance with claim 1 wherein the hydrocarbon-mercapto-hyhydrocarbon phosphites in combination with carbon black drocarbon phosphite is tri(fi-laurylthioethyl) phosphite. of the y used 1n E p 1 aremgorpcrated mto 3. An olefin polymer stabilizer combination in accordples of polyethylene in a manner similar to that described ance with claim 1 wherein the hydrocarbon-mercapto-h Example The Samples J Oven aged at drocarbon phosphite is tri(isooctylthio-tert-butyl) phosexposed to prolonged roll milling at 320 F. as described hi 111 P Q 4. An olefin polymer stabilizer combination in accord- The stabilizers and amounts that are incorporated into ance i h l i 1 h i h hydrocarbon mercapto.hythe Polyethylene are Set forth In Table XVIII belOW- 5 drocarbon phosphite is (monophenylthioethyl) (di-2-eth- TABLE XVIII ylhexylthioethyl) phosphite. Example Carbon mack 5. olefin polymer stabilizer combination in accord- No. Mercapto Phosphite and Amount amount, ance with claim 1 wherein the hydrocarbon-mercapto-hy- Percent drocarbon phosphite is tri(2-ethylhexylthioethyl) phos- 9 Tri(isooctylthiobutyl)phosphite,0.1%".-- 2.5 phite. 2mg;gg fgf giffig ggg 6. An olefin polymer stabilizer combination in accordi ciicii h x gi oi tii i iiio iiita 1.1%-

ance with claim 1 wherein the hydrocarbon-mercapto-hy- 13:3: 1:: Difittttintth filiOSSnttft.n73: 2:5 drqcarbon phosrhlte 1s dlwyclohexvlthwmethyl) P 14. Tri (phenylthiononyl)phosphite,0.1% 2.5 phite. 12:13:: $Eggggfiggggfififfigfi; 25 7. olefin polymer stabilizer combination in accord- 17 T9 osphite ance with claim 1 wherein the hydrocarbon-mercapto-hytfiigitfi ftfifitfgfig ff'fffff 215 drocarbon phosphite is whq y hy p o p REsuL'rs Each combinationh s od stabil'ty aiter it is heat aged in An olefin polymer stablhzer combmatlon m accord- 8, O l 0 an oven for various times up to 292 ho urs at 200 C. and after it is exposed ance wlth clam 1 w l i hydrocarbonmercflpto'hy' to roll milling a 3 for va i times p to 6 hoursdrocarbon phosphite 1S tri(4-tert-butylphenylthioethyl) phosphite. Examples 18 to 26 9. An olefin polymer stabilizer combination in accord- In Examples 18 to 26, three-component stabilizer sysance with claim 1 wherein the hydrocarbon-mercapto-hyterns of the invention containing hydrocarbon-mercaptodrocarbon phosphite is tri(2-methyl-4-tert-butylphenylhydrocarbon phosphites used in Examples 9 to 17, with thioethyl) phosphite. various hindered phenols and carbon black are added to 10. An olefin polymer stabilizer combination in accordsamples of polyethylene as described in Examples 1 and ance with claim 1 including in addition an amount sutfi- 2. The samples are oven aged at 100 C. and exposed to cient to enhance the stabilization of an olefin polymer of prolonged roll milling at 320 F. as described in Exam- 0 a hindered phenol having the formula: ple l.

The stabilizers and amounts that are incorporated into (R),,C (0H),, the polyethylene are set forth in Table XIX below.

TABLE XIX ft in i H d dPh 1 d it oun 1n ere one an gimme l d u ;l l i? 6 percent Amount 18 T is t 1th b l h h't 0.1 2.5 4,4-methylenebis(fi-tert-butyl-o-cresol), 0.05 7. 19 Mii io23%;?lti021i321d$etltlhelthioethyl)phos 2.5 2,2-methy1enebis(B-tei't-butylpheuol), 0.05%. 20 Diicy lohexg lthiomethyl)phosphite, 0.17 2.5 8,5-d1- ert-buty1-4hydroxybenzyl ether, 0.05%. 21- Mono-fi-laurylthioethylphosphite, 0.1% 2. 5 2-ethyl-4-octyl-fi-methylresorcmol, 0.05%. 22 Di(methoxythioethyl)phosphite, 0.1%.-. 2.5 1,3,?)-%rel;1i;i:giy-(2)g%7,6-tris(3,5-dl-tertbutyl-4-hydroxybenzy 23 Tri(phenylthiononyl)phosphite, 0.1% 2. 5 4,4'-cyc1ohexy11den bis(2.6-dl-tert-butyl phenol), 0 05%, 24 Tri(phenylthioethyl)phosphite 2- 5 2,2-methyleneb s(4-ethy1-6-tert-butyl phenol), 0.05%. 25 Tri(4-tert-butylphenylthioethyl) hosphite 2.5 4,4'-methy1enebis(2,ttdi-tertbutyl Phenol), 0.05%. 26 Tri(Z-methyl-4-tert-butylphenylt 'oethyl)phosphi 2.5 4,4-n-b 1ty denebis(Z-tert-fi-methy phenol), 0.05%.

Resume-Each combination has good stability after it is heat aged in an oven for various times up to 292 hours at 100 C. and after it is exposed to roll milling at 320 F. for various times up to 6 hours.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. An olefin polymer stabilizer combination capable of enhancing the resistance of olefin polymers to deterioration in physical properties due to exposure to heat, consisting essentially of a hydrocarbon-mercaptohydrocarbon phosphite having the formula:

OK: in which at least one of the X radicals is R ---(S-A) and the others are selected from the group consisting of hydrogen, R and R -(SA) wherein R and R are organic radicals having from about one to about thirty carbon atoms, selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, alkenyl, cycloalkenyl, alkoxy, aryloxy, and heterocyclic radicals, n

wherein R is an organic radical containing from one to about thirty carbon atoms selected from the group consisting of alkyl, aryl, alkenyl, alkaryl, aralkyl, cycloalkenyl, cycloalkyl, alkoxy, aryloxy and acyl; x is an integer from two to four; x is an integer from one to four; and the sum of x and x does not exceed six; or

(OHM (OH) ene, alicyclene, arylene, and mixed alkylene-arylene and alkylene-alicyclene groups, m is an integer from one to a maximum of (z +y m is zero to three, m is one to about four, Z is one to about five, and y y and 3 are at least one.

11. An olefin polymer stabilizer combination in accordance with claim wherein the hydrocarbon-mercaptohydrocarbon phosphite is tri(phenylthioethyl) phosphite.

12. An olefin polymer stabilizer combination in accord ance with claim 10 wherein the hydrocarbon-mercaptohydrocarbon phosphite is tri(4-tert-butylphenylthioethyl) phosphite.

13. An olefin polymer stabilizer combination in accordance with claim 10 wherein the hydrocarbon-mercaptohydrocarbon phosphite is tri(2-methyl-4-tert-butylphenylthioethyl) phosphite.

14. An olefin polymer stabilizer combination in accordance with claim 10 wherein the hindered phenol has the formula:

OH I- (OHM-l (01m, 6m w l1 2)m J I 0211; 3

wherein R R and R are organic radicals containing from one to about thirty carbon atoms selected from the group consisting of alkyl, aryl, alkenyl, aralkyl, cycloalkenyl, cycloalkyl, alkoxy, aryloxy and acyl groups, Y is selected from the group consisting of oxygen, alkylene, alicyclene, arylene, and mixed alkylene-arylene and alkylene-alicyclene groups, m is an integer from one to a maximum of 5-(z +y m is zero to three, "1 is one to about four, Z is one to about five, and y y and y;; are at least one.

15. An olefin polymer stabilizer combination in accordance with claim 14 wherein the hindered phenol is 4,4- methylenebis- (2,6-di-tert-butyl-phenol 16. An olefin polymer stabilizer combination in accordance with claim 14 wherein the hindered phenol is 4,4- methylenebis 6-tert-butyl-o cresol 17. An olefin polymer stabilizer combination in accordance with claim 14 wherein the hindered phenol is 2,2- methylenebis 6-tert-butyl phenol) 18. An olefin polymer stabilizer combination in accordance with claim 14 wherein the hydrocarbon-mercaptohydrocarbon phosphite is triQQ-Iaurylthioethyl) phosphite and the hindered phenol is 4,4'-methylene-bis(2,6-di-tertbutyl phenol).

References Cited UNITED STATES PATENTS 2,587,616 3/1952 Harman 26030.6 X 3,043,775 7/1962 Cofiield et a1. 252404 X 3,115,465 12/1963 OllOff et a1 252-400 X 3,244,650 4/1966 Hecker et a1 252--404 X OTHER REFERENCES Bevilacqua, E. M., J. American Chemical Society, 1959, p. 5071.

LEON D. ROSDOL, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R. 

